| 摘要 |
The invention prevents execution of unauthorized copies of programs. In one example embodiment, a semiconductor storage device includes a program ROM. A calculator of an address processing unit included in the program ROM processes lower bits (e.g., A0-A7) of a first address from an address bus of a CPU using an address calculation code e.g., (a0-a7) from a code storing unit. The calculator outputs a modified lower address (e.g., A0'-A7'). A selector may selectively replace the original lower address (e.g., A0-A7) with the modified lower address (e.g., A0'-A7') As a result of the replacement, a second address is output from the address processing unit different from the first address.
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